叶尖间隙对小型高速离心风扇气动性能与流场的影响

摘要

A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to the fixed outer casing. Computational models with/without the tip clearance are built and the k-ω shear stress transport (SST) turbulence model and the unstructured mesh are applied to the numerical simulation for unsteady solutions. The overall performance is measured on a standard experimental bench and the major flow feature of each component inside the centrifugal fan is numerically investigated. In the presence of the tip clearance due to the difference of static pressure between leading and trailing edges of the clearance, i. e. , leading and trailing edges of the impeller, a strong return flow exists inside the clearance passage and re-circulates the main stream inside the impeller passage, and produces the strong flow interaction, thus changing the flow field and influencing the overall performance.%针对小型高速离心风扇进行了数值与试验研究.离心风扇封闭叶轮与外机匣之间存在0.7 mm的间隙,叶轮的转速为34 000 r/min.构造了有/无间隙的计算模型,使用k-ωSST湍流模型和非结构网格进行了非定常数值模拟.在一个标准测试平台进行了总体性能的测试,利用CFD技术进行了全三维非定常流场的计算,获得了离心风扇的总体性能和各流动部件的流场结构.由于风扇叶轮与外机匣之间存在的间隙以及叶轮进出口之间的静压差,使得间隙内存在很强的回流,并在叶轮进口处产生很强的流动干涉,从而改变了叶轮进口的流动状况,对离心风扇的总体性能产生很大的影响.